Patent GB-510328-A (GB)
Title: Improvements in abrasive coated articles
IPC: B24D11/00
Filed: 1938-01-28
Abstract: 510,328. Flexible abrasive articles; resinous condensation products. BEHR - MANNING CORPORATION. Jan. 28, 1938, No. 2839. Convention date, Feb. 6, 1937. [Class 60] [Also in Group IV] Coated abrasive articles are made by forming on a backing a binder layer of a synthetic resin, controlling the viscosity of the resin to enable it to trap abrasive grains, applying the abrasive grains, controlling the viscosity of the binder to prevent flow thereof or movement of the abrasive grains, initially drying and curing the resin by raising the temperature so that the viscosity of the binder increases at a rate equal to or greater than the decrease in viscosity due to the increase of temperature until the resin becomes brittle and a tensile strength above 6,000 pounds per square inch is developed. Condensation products of phenol, cresol or urea with formaldehyde or hexamethylene tetramine or alkyd resins may be used. The adhesive film may be increased in viscosity prior to application of abrasive by loss of solvent, fall in temperature, further condensation or by a combination of these means. A flow test for controlling the critical drying and curing cycle is described. Suitable resins are made by (1) heating together phenol and solid sodium hydroxide at 212-230‹F, cooling to 122‹F and adding formaldehyde, paraformaldehyde or hexamethylene tetramine and heating to 248‹F; (2) heating at lower temperatures under vacuum to produce a lower viscosity resin; (3) heating phenol, formalin and barium hydroxide at 140-148'F, applying a vacuum of 25-28'', continuing heating at 230‹F until a drop in ice water is brittle and adding alcohol to dissolve; (4) neutralizing 2.25 mols of formaldehyde with sodium carbonate solution, refluxing and adding 1 mol of urea in hot water with formic acid to a p.H. of 4.7, after which a formic acid-sodium formate buffer is also added and the mixture refluxed and dehydrated under vacuum to a viscous syrup. The temperature of the resin at application may be from 75-175‹F, the abrasive may be heated to a temperature of 100-160‹F to assist trapping, and the drying and curing cycle for the resin may extend over the range 75- 300‹F. The initial curing temperature should not exceed 160‹F. Paper or cloth from a roll 10 is coated by rolls 11 with adhesive 13 comprising 75 per cent. resin and 25 per cent. solvent supplied from a jacketed tank 14. Abrasive grains are applied from a hopper 17 by means of the electrostatic field A, B as described in Specifications 378,014, 379,379 and 398,907. From roll 21 the web passes horizontally for the period of time required for the resin to attain the viscosity necessary to support the grains and is taken by suction drum 22 to a drying room where it is cured' for one hour at 75'F, 18 hours at 160‹F followed by hour at 284‹F. A sizing coat, for example an alcohol solution of a synthetic resin, is then applied and similarly cured. In a modification a compound backing is used as described in Specification 510,330 to produce heavy metal cutting discs and in this case the abrasive is applied direct from the hopper and is pressed into the adhesive by rolls. Specifications 510,329, 510,331 and 510,332 also are referred to.